Exploding Galaxies and the Brightest Objects in the Universe

Exploding Galaxies and the Brightest Objects in the Universe

Exploding Galaxies and the Brightest Objects in the Universe

Exploding Galaxies and the Brightest Objects in the Universe

In 2013, scientists attempted to recreate

the evolution of the universe from shortly

after the Big Bang until today.

This simulation, which took 19 million CPU

hours to produce started with a predicted

amount of matter, dark matter, and dark energy

that should have existed shortly after the

Big Bang.

The simulation was allowed to run to see if

these parameters that were set at the beginning

can produce the galaxies and the universe’s

the structure we see today.

What you are looking at here is limited to

a 32 million light year cube of the simulation,

the expansion of the universe considered,

with simply gas density and temperature visible.

This is the intergalactic medium.

Even though space is a vacuum, there are still

a few particles in every cubic centimetre

of space.

Blues are the coldest regions here; whites

are the hottest.

As gas particles are drawn together by their

own gravity and that of dark matter, the gas

clumps and over the course of millions of

years, coalesces into galaxies, which increases

the gas’s temperature drastically.

What you’ll immediately notice is that there

appear to be explosions coming from the densest


But galaxies exploding?

That can’t be right, I surely would have

heard of that before.

Remember, this is just the intergalactic gas

the temperature we are seeing, and each second

passing in the video is a few million real

time years.

Quasars, or extremely active black holes, are

the brightest objects in the universe, emitting

more electromagnetic radiation than entire

galaxies combined.

When a Quasar lights up, its rapid increase

in radiation blasts into space ionises the

intergalatic gas as it expands out, heating

it up to extreme temperatures.

This is known as quasar-mode, or Active Galactic

Nuclei feedback.

Black holes don’t remain as quasars for lengthy

periods of time, rather quasars, are the result

of a large amount of mass falling into them,

lighting them up and causing them to eject

huge amounts of mass and energy.

They’ll remain quasars as long as there

is matter being fed into them.

Although, you may wonder, how can a black

hole emit anything?

Don’t they absorb it all?

And the answer is yes.

It is in fact the accretion disk around the

quasar that is so energetic and luminous.

A black hole’s accretion disk is the result

of matter passing by being ripped apart and

sucked into orbit.

These supermassive black holes often have

billions of solar masses, the gravity around

them is immense.

As the material in the accretion disk orbits

and falls inwards, the friction from the material

in the disk rubbing together creates energy

so intense that a quasar can be thousands

of times brighter than our Milky Way.

In fact, a quasar’s host galaxy is often

too dim to detect next to the bright quasar,

although techniques with the Hubble Space

Telescope has allowed a few of these host

galaxies to be seen too.

Quasars could light up from collisions of

galaxies, when suddenly an abundance of matter

falls into a supermassive black hole, although

this doesn’t always happen.

You’ll also notice these jets coming from

the quasar’s poles, these extend well beyond

the galactic disk, and can even be seen illuminating

other galaxies and dust clouds like a spotlight.

Quasars themselves are bright, but when these

jets are pointed towards us, they are known

as Blazars.

The jets are believed to be powered by the

black hole’s magnetic structure, and they

can carry high energy plasma away from the

black hole at almost the speed of light.

The days of Quasars and Blazars are thought

to be over, the closest Quasar to us is 600

million light years away, and thus was going

on 600 million years ago.

However, you’ll notice that the explosions

in the simulation don’t let up in this video

as time passes.

This comes from the last in the Active Galactic

Nuclei family of black holes, radio galaxies.

Typical Quasars and Blazars are so bright

that they light up in all frequencies of the

electromagnetic spectrum uniformly, radio

galaxies originate from black holes that,

unsurprisingly, are brighter in radio wavelengths.

These explosions now come from radio galaxies,

and this is known as radio mode feedback.

The simulation stops at the present day.

Now, while impressive, the simulation isn’t


For instance, it could only simulate a trillion

particles compared to the countless number

of particles in the equivalent section of


Also, we don’t have a perfect knowledge

of the parameters of the universe, and so

there were certain mistakes evident in the

model like the overprediction of star formation.

There are plans to try this again at some

point with an updated understanding.

Being able to model how the universe evolved

can give us confirmation about how we believe

it formed, and this is of great interest to


Let’s see what future results will bring!

So, can galaxies explode?

Not in the conventional sense, but if you

are talking about exploding with electromagnetic

radiation, then absolutely. 

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